Abstract

The fundamental frictional behaviour of carbon fibre tows relevant to composite fabric forming is explored. Tow-on-tool and tow-on-tow contact are considered. For tow-on-tool contact, an experiment is devised to simultaneously observe the true filament contact length and measure the friction force over a range of normal loads. Filament contact length is not constant, as would be given from an idealised assumption of parallel touching filaments, but increases in a characteristic manner with normal load. Friction force follows a power law variation with normal load with exponent in the range 0.7–1. Accounting for the evolving contact length in a Hertzian calculation of the real contact area produces a contact area versus load variation which differs only by a constant factor from the measured friction force curves. Thus, the results agree with a ‘constant interface strength’ model of friction. Tow orientation and sizing are found to have a significant effect on friction by altering the real contact area.

Item Type:

Articles

Additional Information:

The authors would like to acknowledge the assistance of the
Engineering and Physical Sciences Research Council (EPSRC) for
supporting the present work under grant Ref. EP/K032798/1 (Friction
in Composites Forming). We would also like to acknowledge
the contribution of our industrial collaborators at Jaguar Land
Rover and Granta Design Ltd, as well as our academic partners
from the Composites Research Group at the University of Nottingham
(Dr Endruweit and Profs. Long, Warrior and De Focatiis). Hexcel
UK are thanked for supplying the tow material. The detailed
data relating to this paper can be accessed at the following Cambridge
Data Repository: http://dx.doi.org/10.17863/CAM.1671.